TE technology is based on the concept that a temperature differential may be converted into electricity and vice versa. Namely, the Seebeck effect is the conversion of a temperature differential directly into electricity, and the Peltier effect is the production of a temperature differential from a difference in electric potential.
TE modules hold great promise for widespread use due to their solid state structure, silent operation, high reliability and long service life. TE modules used for power generation can produce electricity from virtually any source of heat, which could enable many energy conversion processes to increase efficiency, reduce pollutant emissions and lower costs. TE modules used for heating or cooling can achieve very sensitive temperature control, and TE modules used for cooling do not require volatile working fluids.
The conventional bulk die design for TE modules in the prior art is shown in FIGS. 1 and 2. FIG. 1 shows the exterior of such a TE module 10. FIG. 2 shows interior of TE module 10, including the thermoelectric elements 20, the electrical conductors 22 affixed on the ends of the thermoelectric elements 20, and the electrically insulating substrates 24. This design suffers:                1. Need for additional heat transfer equipment when gas or liquid mediums are used as the heat source and or heat sink. This need also results in large thermal contact resistances across mating surfaces between heat exchanger and TE module (10-15° C. loss on each side is typical). Further, this need also creates an excessive thermal path length, adds considerable mass to the overall system, and is difficult to integrate with existing heat exchange processes,        2. Long electric current path and resulting high Ohmic loss        3. Difficult and expensive component manufacture and module assembly,        4. Limited module size due to excessive thermal stress, and        5. Limitations on soldered designs to temperatures below 225° C.        
Improvements in TE material production methods resulted in the conventional thin film design, as shown in FIG. 3. This TE module 30 comprises thin film thermoelectric elements 32, electrical conductors 34 on the tops and bottoms of the thermoelectric elements 32, and electrically insulating substrates 36. This design can make use of new thermoelectric material and has a much shorter electric current path than the conventional bulk die design, resulting in a reduction in Ohmic loss. However, the thinner thermoelectric elements result in increased difficulty in maintaining a sufficient temperature gradient across the thermoelectric elements. In addition, the conventional thin film design also suffers from the other disadvantages listed for the conventional bulk die design.
As a result, another thin film design has been developed, as shown in FIG. 4. This TE module 40 comprises thin film thermoelectric elements 42, electrical conductors 44 affixed to the ends of the thermoelectric elements 42, and electrically insulating substrates 46. This design has the advantages of the conventional thin film design and can withstand large temperature gradients without generating excessive thermal stress. It also has simple component manufacture and assembly. However, it still suffers from the need for additional heat transfer equipment to transfer effectively heat to and or from gas or liquid mediums via convection. It also uses thermoelectric material inefficiently and has significant limitations on stack length.